Heliostat drive-structure mechanical interface

ABSTRACT

A mechanical interface between the drive and support structure of a heliostat assembly for use in concentrated solar power applications. The heliostat drive is mounted to the support structure by inserting a drive post into a structure post, the structure post having grooves for interfacing with bolts or other fasteners attached to the drive post. The structure post has a plurality of grooves to allow for multiple heliostat orientation options. The heliostat assembly further includes a capsule containing a drive motor controller and cable-mounting features, wherein the capsule is inserted into the drive post and has a cable-positioning feature to provide egress of power and communication connectors from the drive through at least one groove.

CROSS-REFERENCES TO RELATED APPLICATIONS

The present application claims priority to and the benefit of U.S.Provisional Patent Application No. 61/880,739, filed on Sep. 20, 2013,the entire disclosure of which is incorporated herein by reference.

BACKGROUND OF THE INVENTION

This disclosure relates generally to heliostats having reflectorsconfigured to redirect sun light to a target or receiver, and inparticular to the mechanical interface between a heliostat driveassembly configured to orient the reflector and the structure upon whichthe drive is mounted.

In Concentrating Solar Power (CSP) plants, arrangements of heliostatsreflect sunlight toward a receiver mounted atop a tower containing aworking fluid. One type of receiver transfers incident radiant energy tothe working fluid to produce high-pressure, high-temperature steamthrough the means of a heat exchanger or a phase change of the workingfluid itself. The working fluid can be water, air, or a salt materialheated to a molten state. The output steam can facilitate a variety ofapplications, such as electrical power generation, enhanced oilrecovery, and desalination. Heliostats are generally mounted on theground in an area facing or surrounding the receiver tower. Eachheliostat has a reflector: a rigid reflective surface, such as a mirror,that tracks the sun through the actuation of a heliostat drive mechanismabout at least one axis. Sun-tracking involves orienting the reflectorthroughout the day so as to optimally redirect sunlight from the suntoward the receiver and maintain the desired temperature of the workingfluid.

One approach to constructing a heliostat field is to utilize a smallamount of comparatively large heliostats (e.g., greater than between 50and 150 m²). In such a power plant, having a fewer number of heliostatsmay necessitate the manufacture of very precise, and thus veryexpensive, components for the positioning of the reflective surfaces.Another approach, however, is to use a large amount of comparativelysmall heliostats (e.g., between 1 and 10 m²), such as with reflectivesurfaces that measure between 1 and 3 m on each side. Such an approachmay be more efficient at redirecting sun light because there are moreindividually adjustable reflective surfaces. In addition, smallerheliostats may be cheaper to produce and easier to assemble, decreasinginstallation time and operations costs. However, a plant comprising moreheliostats will necessarily require the same amount of additional driveassemblies, increasing the number of repeated steps during installation.Accordingly, there is a need for heliostat assemblies that are botheconomical to manufacture and efficient to install.

A major cost driver in CSP plants is the cost of manufacturing,installing, and maintaining the components of the heliostat fields.Heliostat fields are typically deployed by installing ballastfoundations into the ground and mounting the heliostats and reflectorsthereto. Installing these ballast features may require significantground preparation and heavy machinery, for example to dig holes of asuitable depth for structure posts. Deploying a plurality of heliostatsmay also be very time consuming if separate ballasts must be installedfor each heliostat assembly, and the requisite labor can be a majorcontributor to operations and maintenance costs. If the interfacebetween the heliostat and the ballast or structure to which it ismounted is complex, this can increase the time it takes to remove orreplace heliostats in need of repair. Additionally, heliostats requirepower and data distribution means for actuation and control. Power anddata is typically distributed to a heliostat drive via power and datadistribution cables that may be routed through conduit, the ballast, orelements of the mounting structure. Feeding wires and cables throughballasts or structures may require additional setup time whenever aheliostat is installed or removed. This additional setup time becomescompounded during the installation or maintenance of a field comprisinga plurality of heliostats, impacting labor costs. Accordingly, there isa need for heliostats having a drive assembly and mounting structurethat are designed to minimize installation and replacement times.

SUMMARY OF THE INVENTION

Improved heliostat assemblies are described herein, wherein theassemblies are configured to facilitate rapid and repeatableinstallation (or removal) of heliostat drives onto (or from) heliostatstructures. The improved heliostat assemblies thereby reduceconstruction and maintenance costs by reducing labor time and the meantime to repair a heliostat. To provide these advantages, the heliostatstructures and drives may comprise compatible mechanical interfacefeatures that facilitate the installation of heliostat drives ontoheliostat structures in one of a plurality of optional orientationsutilizing a minimum of fasteners. In addition, the heliostat structuresand drives may comprise cable management features for routing heliostatpower and data cable connectors for convenient access to field power anddata distribution cables. The heliostat assemblies of the presentinvention thereby obviate the need to route power and data distributioncables through heliostat ballasts or ground-mounted structures, reducingthe time to install and remove units.

Heliostat assemblies according to an embodiment of the present inventionmay comprise: a drive chassis comprising a drive post having a groove,and a structure comprising a structure post having an alignment feature,wherein the drive post is inserted into the structure post and isaligned via the alignment feature. The alignment feature of thestructure post may comprise a first tube end having a plurality ofgrooves, wherein the grooves are spaced equidistant from each other byan offset angle and define multiple heliostat drive orientationsrelative to the structure post. The drive post may further comprise asecond tube end having a groove. The drive post attaches to thestructure post via a plurality of fasteners that fit into the grooves ofthe alignment feature. The plurality of fasteners are spaced equidistantfrom each other by an offset angle such that the drive chassis can beinstalled in any of the multiple heliostat drive orientations as definedby the grooves of the alignment feature. The structure post may furthercomprise a contacting region having a smaller diameter than the firsttube end, wherein the drive post makes contact with the contactingregion.

The heliostat assembly may further comprise a capsule inserted into thedrive post, wherein the capsule contains cable-mounting components andelectronics components. The cable-mounting components may comprise cableconnectors that egress from the capsule. The capsule may comprise acable-positioning feature having a protrusion that orients thecable-mounting components at an acute angle relative to the capsule. Theprotrusion may be positioned within the groove of the drive post andwithin a groove of the alignment feature. The protrusion is furtherpositioned between at least two of said plurality of fasteners and isspaced equidistant from said fasteners by an offset angle.

These and other features and advantages of the present invention arediscussed or apparent in the following detailed description of theinvention in conjunction with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1A is a perspective view of a heliostat drive assembly and aheliostat structure;

FIG. 1B is a perspective view of the heliostat drive assembly before itis inserted into a post of the heliostat structure;

FIG. 1C is a perspective view of the heliostat drive assembly after ithas been inserted a post of the heliostat structure;

FIG. 2A is a side view of a structure post without a drive assemblyinstalled;

FIG. 2B is a side view of the drive assembly comprising an electronicscapsule installed in the structure post of FIG. 2A;

FIG. 2C is a bottom cut-away view of a heliostat drive assemblyinstalled in the structure post of FIG. 2A;

FIGS. 3A-3F are top cut-away views of a heliostat drive assemblyinstalled in the structure post of FIG. 2A in six differentorientations;

FIG. 4A is a side view of the mechanical interface between the heliostatdrive assembly and the heliostat structure;

FIG. 4B is a side view of the heliostat drive assembly installed in thestructure post;

FIG. 4C is a side view of a contacting feature inside the structurepost;

FIG. 5A is a perspective view of the drive post with the electronicscapsule inserted therein; and

FIG. 5B is a perspective view of the electronics capsule of FIG. 2B.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

An improved heliostat assembly is described herein, with reference toFIGS. 1-5. The exemplary heliostat assembly is advantageously configuredto provide for a mechanical interface between a heliostat drive and amounting structure that is quick to install and provides convenientaccess to cable-mounting components.

A heliostat assembly according to an embodiment of the present inventionmay comprise at least one heliostat drive installed onto a heliostatstructure, as illustrated in FIGS. 1A-1C. A heliostat structure 101 maycomprise structure posts 110 connected by cross members 111, whereineach of the structure posts may be connected to one another by at leastone cross member. A heliostat drive 130 may be installed in eachstructure post 110. The heliostat drives are configured to rotate areflector (not shown) about at least one axis, the reflector beingmounted to the drive via a reflector channel 114. The structure may berooted to the ground via a ground interface feature 112. The groundinterface feature 112 may comprise stakes embedded in the ground or in afoundation, or may comprise weights or a ballast material. The structuremay be formed from a suitably rigid and corrosion-resistant material,such as a steel alloy. The drive may be mounted to the structure byphysically inserting the drive post 160 into the structure post 110. Thestructure post may comprise an alignment feature 113, such that thedrive post 160 can only be installed in an orientation selected from aplurality of orientations defined by the alignment feature. FIG. 1Billustrates the drive prior to installation in the structure post andFIG. 1C illustrates the heliostat assembly post-installation.

The alignment feature 113 may comprise a plurality of grooves 200 thatallow for mounting of the heliostat drive, as illustrated in FIG. 2A. Inthe illustrated embodiment the structure post has six grooves, althoughit may have more or less grooves depending on system requirements. Thestructure post grooves 200 define a plurality of possible heliostatdrive orientations, each orientation being offset by an angle ofrotation. The alignment feature may have a first tube end, wherein thegrooves 200 are set equidistant from each other around the circumferenceof the first tube end. In the illustrated embodiment the six adjacentgrooves 200 are separated from each other by an angle of sixty degrees.The first tube end may be either made integral with the structure post,or it may be a separate part that is placed on top of the structurepost. The alignment feature 113 may also comprise an intermediatetapered segment 115 between the first tube end and the remainder of thestructure post 110. The tapered segment 116 has smaller diameter thanthe remainder of the structure post and serves to increase the stabilityof the structure when subjected to transverse loads.

A capsule 150 may be inserted into the drive post 160, and the drivepost may be inserted into the structure post 113, as illustrated in FIG.2B. The capsule may comprise cable-mounting components 170 forconnecting to power and data transmission cables. The cable-mountingcomponents may egress from the capsule 150 and may be routed through oneof the plurality of grooves 200. The drive post 160 is fixedly attachedto the structure post 113 via a plurality of fasteners 210. Thefasteners may comprise bolts, screws, or other suitable means ofattachment. In the illustrated embodiment, the drive post is fixedlymounted within the structure post 113 by tightening three bolts 210.

A cable-positioning feature 320 may be made integral with the capsule150 to allow cable-mounting components 170 to exit the structure post113, as illustrated in FIG. 2C. The cable-positioning feature fitswithin a groove 200 not occupied by any of the fasteners 210. Nuts 250may be included in the capsule 150 to provide for mounting of the drivepost 230 to the structure post 110 by tightening the bolts 210. The nutsmay be of a square shape to limit slippage or loosening within the drivepost. The fasteners may be offset from each other by an equidistantangle. In the illustrated embodiment, for example, the three fastenersare each offset by 120 degrees. The cable-positioning feature may be setbetween at least two of said fasteners and may be spaced equidistantfrom said fasteners by an offset angle, such as 60 degrees.

The locations of the grooves 200 define multiple orientations of theheliostat drive when mounted on the structure, as illustrated in FIGS.3A, 3B, 3C, 3D, 3E, and 3F, each depicting a different installationorientation. For example, having six grooves positioned around thecircumference of the alignment feature allows for the heliostat drivesto be orientated in any of six positions. FIGS. 3A-3F show how theheliostat can be set to different orientations to face in differentinitial directions, as indicated by the arrow. As described above,fasteners 210, such as bolts, may be used to hold the drive tube inplace when inserted into a structure post 110. In the depictedembodiment, the threaded portions of the bolts 210 fit within thegrooves 200 of the alignment feature and the bolt heads grip thealignment feature when tightened, fixedly attaching the drive post tothe structure post. The present embodiment allows for heliostats to berepeatedly installed onto structures using basic hand tools withinminutes. Because the heliostats can be installed in differentorientations and then be actuated to a desired facing, the presentinvention eliminates the need to orientate all newly installed driveswith respect to a certain direction, which can reduce installation time.

The drive post 160 of the drive assembly 130 may further comprise asecond tube end and a groove 170, as illustrated in FIG. 4A. The groove170 may extend from the second tube end of the drive post up towards thedrive chassis 180. The groove may be sized to be wider than thepositioning feature 320 of the capsule 150 (see FIGS. 2B and 2C). Wheninstalled, the drive post groove 170 may align with one of the alignmentfeature grooves 200, as illustrated in FIG. 4B.

The structure post may further comprise a contacting feature 270 at theboundary between the alignment feature 113 and the tapered segment 115,as illustrated in FIG. 4C. The contacting feature 270 may comprise anindented segment of the structure post that contacts the side of thesecond tube end when it is installed, or it may comprise a ledgeinternal to the tube that contacts the bottom of the second tube endwhen it is inserted into the first tube end of the structure post.Alternatively, the structure post may have two or more diameters or wallthicknesses such that the internal diameter of the structure post at thecable-positioning feature is smaller than the internal diameter of thestructure post at the alignment feature or at the base of the structurepost. In this way the contacting feature creates contact between thesecond tube end of the drive post 160 and the inside of the structurepost 110. The drive post 160 may rest on the contacting feature 270 suchthat the fasteners 210 do not make contact with the bottom of thegrooves 200. This design thereby facilitates the quick alignment offasteners 210 in the grooves 200 and allows for easy tightening of anybolts being utilized. The sizes of the contacting feature, the drivepost, and the structure post can be configured to increase the stiffnessof the system.

A capsule 150 may be inserted inside the drive post 160 as illustratedin FIGS. 5A and 5B, wherein the capsule may be used to house electronicsand facilitate the egress of power and data distribution cables 170. Thecapsule may be designed to fit inside the drive post and may be removedfor maintenance or replacement. The electronics may supply control,instrumentation, health monitoring, and calibration functions to theheliostat. A capsule 150 as shown in FIG. 5B may comprise cable-mountingcomponents, attachment nuts 310, and electronics for heliostat control,such as a motor controller board (not shown). The capsule may furthercomprise a cable-positioning feature 320 that provides strain relief toemergent cable-mounting components and reduces the likelihood of cabledamage from cable movement. The cable-positioning feature may comprise aprotrusion sized to fit within the groove 170 of the drive post andwithin any of the grooves 200 of the alignment feature. The heliostatmay therefore be positioned in any configuration that allows forsimultaneous mating of the fasteners with the structure grooves and theprotrusion with a structure groove not mated with a fastener. Theprotrusion may be set at an angle to provide protection from rain andwashing; this angle may be an acute angle relative to the capsule.

The capsule 150 may further comprise recessed portions into which thenuts 310 are embedded. The nuts may be threaded to interface with thefasteners of the drive post. In this way the same fasteners are used tostabilize the capsule within the drive post and fixedly mount the drivepost to the structure post.

The cable-mounting feature 170 may comprise two cable ends, for examplea female cable end 190 and a female cable end 195. The cable ends egressfrom the capsule and are guided by way of the cable-positioning feature320 through the groove 170 of the drive post and a groove 200 of thealignment feature 113 at the end of the structure post. The cable endsmay be of different lengths for easy identification; for example thefemale cable end may be longer than the male cable end. The cablepositioning feature may also orient the cable ends 190 and 195 at anangle relative to the capsule via a protrusion.

Each heliostat assembly may additionally comprise a data and powerconnection for directing the drive to a desired orientation. The powerconnection may supply an energy path to a motor controller board of theheliostat drive. The motor controller board may transmit power to theelectrical components of the drive assembly, such as motors that driveat least one transmission. The data connection may provide communicationand control pathways to the heliostat drive control boards from acentral or distributed controller or network. The power and dataconnections may comprise, for example, cables or wires that connect tothe control board housed within the capsule.

Two inter-drive cables (not shown) may be connected to the cable-mounting components that egress from the capsule through the drive postgroove and an alignment feature groove. The inter-drive cables may beused to connect the heliostat to other heliostats in the field, in thisway power and/or data can be transmitted to heliostats connected inseries. The inter-drive cables may be pre-wired to the cable managementcomponents, or they may be installed on site. One method of configuringthe inter-drive cables is to provide one long cable and one short cablefor each heliostat drive. The long cable may be configured to havesufficient length to reach the short cable of an adjacent heliostatdrive on the same or neighboring structure. The inter-drive cables andcable-mounting components may be coated with material to enhance theirlifetime when exposed to environmental conditions, such as a UV coating,plastics, metals, or other materials that can delay or prevent cabledegradation.

Inter-drive cables may be attached to the structure with the use of oneor more fastening devices. Potential fastening devices may include twistties, clamps, clips, wires, adhesives, or another suitable method ofattaching the cables to the structure. These fastening devices may helpto minimize the movement of the cable in wind, and also act as strainrelief by keeping the cables affixed to the structure.

When connecting inter-drive cables between heliostats, the cable may beleft to hang between structure posts, or it may be held off the groundby a supporting feature. Examples of supporting features may include awire, a rigid member, a flexible member, a slot, or an enclosed tube.The supporting feature be made integral with the structure or installedthereon. A supporting feature may be used to provide strain relief whena cable is run from one heliostat structure to another and may be madeof a variety of materials, including but not limited to: metal, plastic,composites, or string. Alternatively, cables may be routed along thecross members between structure posts.

Various combinations and/or sub-combinations of the specific featuresand aspects of the above embodiments may be made and still fall withinthe scope of the invention. Accordingly, it should be understood thatvarious features and aspects of the disclosed embodiments may becombined with or substituted for one another in order to form varyingmodes of the disclosed invention. Further it is intended that the scopeof the present invention herein disclosed by way of examples should notbe limited by the particular disclosed embodiments described above.

We claim:
 1. A heliostat assembly for dynamically adjusting the positionof a reflector, the heliostat assembly comprising: a drive chassiscomprising a drive post; a structure comprising a structure post havingan alignment feature, wherein the drive post is inserted into thestructure post and is aligned via the alignment feature.
 2. Theheliostat assembly of claim 1, wherein the alignment feature comprises afirst tube end having a plurality of grooves.
 3. The heliostat assemblyof claim 3, wherein the grooves are spaced equidistant from each otherby an offset angle and define multiple heliostat drive orientationsrelative to the structure post.
 4. The heliostat assembly of claim 3,wherein the offset angle is 60, 120, or 180 degrees.
 5. The heliostatassembly of claim 3, wherein the first tube end comprises six grooves.6. The heliostat assembly of claim 2, wherein the drive post attaches tothe structure post via a plurality of fasteners that fit into thegrooves of the alignment feature.
 7. The heliostat assembly of claim 6,wherein the plurality of fasteners are spaced equidistant from eachother by an offset angle.
 8. The heliostat assembly of claim 6, whereinthe structure post further comprises a contacting region having asmaller diameter than the first tube end, and wherein the drive postmakes contact with the contacting region.
 9. The heliostat assembly ofclaim 6, further comprising a capsule containing cable-mountingcomponents and electronics components, wherein the capsule is insertedinto the drive post.
 10. The heliostat assembly of claim 9, wherein thecable-mounting components comprise a female cable connector and a malecable connector that egress from the capsule.
 11. The heliostat assemblyof claim 9, wherein the electronics components comprise a motorcontroller configured to actuate the heliostat to move to a desiredposition.
 12. The heliostat assembly of claim 9, wherein the capsulefurther comprises a cable-positioning feature.
 13. The heliostatassembly of claim 12, wherein the cable-positioning feature comprises aprotrusion that orients the cable-mounting components at an acute anglerelative to the capsule.
 14. The heliostat assembly of claim 13, whereinthe drive post further comprises a second tube end having a groove, andwherein the protrusion is positioned within said groove.
 15. Theheliostat assembly of claim 14, wherein the protrusion is positionedwithin a groove of the alignment feature.
 16. The heliostat assembly ofclaim 15, wherein said protrusion is positioned between at least twofasteners and is spaced equidistant from said fasteners by an offsetangle.
 17. The heliostat assembly of claim 9, wherein the capsulecomprises at least one recessed exterior surface.
 18. The heliostatassembly of claim 17, wherein a plurality of nuts are positioned withinthe recessed exterior surfaces of the capsule, and wherein the nutsinterface with said fasteners.